The present invention concerns an arrangement of lighting apparatus in a vehicle.
More particularly, the present invention relates to an arrangement of lighting apparatus in a motor vehicle comprising a left hand headlight and a right hand headlight arranged in the front of the vehicle, the apparatus being of the type in which each headlight comprises a reflector of the type having a complex surface of concave, generally parabolic form, the geometry of which is optimised for the short range, or dipped beam, or passing beam function.
A lamp, arranged inside the reflector, comprises a filament for the dipped beam function and a filament for the main beam function. The dipped beam filament is arranged generally on the main axis of the lamp which is oriented towards the front. This axis is substantially horizontal and parallel to the longitudinal direction of the vehicle, while the main beam filament is arranged generally on a secondary axis parallel to the main axis and offset radially from the latter. The position of the main beam filament is defined by its angular position with respect to a position of origin situated in a vertical plane containing the main axis, below the dipped beam filament, and along a circle centred on the main axis and oriented positively in the trigonometric direction as seen looking forward along the main axis.
A new normalised type of double filament lamp, without a masking cup, of the xe2x80x9cH13xe2x80x9d type, has been developed for equipping vehicle headlights in order to satisfy legal requirements on vehicle lighting, especially in the United States and Europe. This type of lamp has two substantially parallel filaments, one for the dipped beam function and the other for the main beam function.
This type of lamp is arranged in a vehicle projector which is optimised to give the dipped beam function and which includes a complex surface reflector.
The complex surface reflector is a reflector in which the reflective surface consists of a large number of portions of parabolas which are so oriented that the headlight produces a regulation dipped beam. Such a dipped beam is characterised in particular by a xe2x80x9ccut-offxe2x80x9d, that is to say a directional limit above which the only light intensity emitted has little or no ability to dazzle. The cut-off consists generally of a horizontal half plane, which lies to the left of the longitudinal axis of the headlight for driving on the right hand side of the road, and a half plane which is slightly inclined upwards, to the right of the said longitudinal axis. This last mentioned half plane is raised by a so-called cut-off elevation angle which is 15xc2x0 for a normalised European beam.
The lighting produced by such a beam on a screen placed about 25 meters in front of the headlight is shown in FIG. 1 of the accompanying drawings (which is described in the section xe2x80x9cBrief Description of the Drawingsxe2x80x9d later in this specification). Referring to FIG. 1, the point HV is the projection of the optical axis of the headlight at the intersection of the vertical plane vxe2x80x2v with the horizontal plane hxe2x80x2h. The cut-off is defined by the straight line Ox which lies parallel to, and below, the horizontal axis hxe2x80x2h, which extends from the point O towards the left, and by the line Oy, inclined at 15xc2x0 and extending from the point O upwards and to the right.
The main beam is generally centred on the point HV, where its light intensity is required to be at a maximum.
It will be noted that this description is made with reference to a vehicle designed for driving on the right. For a vehicle driving on the left, it is sufficient to consider the drawings as showing the screen or the headlight reversed about the axis vxe2x80x2v.
When the headlight is operating in dipped beam mode, it is found that the light emitted by the dipped beam filament is reflected on the main beam filament which is situated close to the dipped beam filament. This causes parasitic light rays to be emitted outside the dipped beam, and in particular above the cut-off. These parasitic light rays can dazzle the drivers of vehicles travelling in the opposite direction, in the left hand lane.
In addition, the main beam filament is arranged in the emitting zone of the dipped beam filament so that it gives rise to shadow zones or reduces the light intensity in some illuminating zones of the dipped beam.
When the headlight is working in main beam mode it is necessary that the light intensity of the illuminating beam produced by the main beam filament is at a maximum at the point HV.
In current practice, the lamp holder is arranged in an identical way in both the left hand and right hand headlights, so that the main beam filament is arranged at about +50xc2x0 with respect to the position of origin on the circle defined above. This angular position enables a dipped beam and a main beam to be obtained which conform with the regulations.
However, this angular position does represent a compromise which does not lead to optimum headlight efficiency. In particular, in main beam mode, the headlight does not make sufficient use of the maximum lighting capacities of the main beam filament. The main beam is offset sideways.
An object of the invention is to overcome the above mentioned drawbacks, and to propose a vehicle headlight that gives a more efficient main beam, while conforming with the regulations.
According to the invention, lighting apparatus of the type defined under the heading xe2x80x9cField of the Inventionxe2x80x9d above is characterised in that the angular position of each main beam filament lies in the range between xe2x88x9290xc2x0 and +90xc2x0, and in that the angular position of the main beam filament of the left hand headlight is different from the angular position of the filament in the right hand headlight.
The angular positions of the two main beam filaments are preferably of opposite signs. In this connection, the angular position of the main beam filaments of the left and right hand headlights may be of negative and positive signs respectively, or of positive and negative signs respectively.
The absolute value of the angular position of positive sign is equal to about 60xc2x0, and the absolute value of the angular position of negative sign is equal to about 40xc2x0.
Further features and advantages of the invention will appear more clearly on a reading of the following detailed description of a preferred embodiment of the invention, which is given by way of non-limiting example only and with reference to the accompanying drawings.